get_mainline_person_distance

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations, the description carries the full burden. It discloses the update schedule (monthly, M-2) which is useful for data freshness expectations. However, it does not explicitly state that the tool is read-only or describe any side effects, though '통계' (statistics) implies a query operation. The return format is covered by the output schema, so not required here. The disclosure is partial but not misleading.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single sentence with the core purpose, followed by a compact parameter legend. It is perfectly front-loaded with the key information and contains zero fluff. Every character earns its place.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

The output schema is present, so return format is covered. The description gives purpose, update frequency, and parameter meanings, which is good for a simple 2-param query. However, it does not clarify default behavior when parameters are omitted (e.g., returns all routes or all months), which is a plausible usage scenario given the optional params. This is a minor gap but leaves some ambiguity.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 0%, so the description fully compensates by explaining both parameters: run_ym is the operating year-month in YYYYMM format, and rte_nm is the route name. This is exactly the needed context for an agent to construct valid calls. The default empty strings are not explained, but that's minor given the explicit format for the main usage.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description states the resource clearly: 'Mainline train route distance statistics'. This distinguishes it from sibling tools by naming the specific metric (person distance) and the entity (mainline route). However, it does not explicitly differentiate from other mainline statistics tools (e.g., get_mainline_route_per, get_mainline_distance_per), so it's clear but not fully distinct.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

No guidance is given on when to use this tool versus alternatives. It does not mention any conditions, exclusions, or why one would choose this over sibling stats tools. The update frequency hints at data freshness but does not help with selection. This is a significant gap for an agent deciding between many similar get_mainline_* functions.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.